Image forming apparatuses are used as printers, facsimile machines, copiers, plotters, or multi-functional devices having two or more of the foregoing capabilities. As one type of image forming apparatus, image forming apparatuses employing a liquid-ejection recording method are known that use a recording head(s) to eject droplets of ink or other liquid. During image formation, such liquid-ejection-type image forming apparatuses eject droplets of ink or other liquid from the recording head onto a recording medium to form (record or print) a desired image on the recording medium.
Such liquid-ejection-type image forming apparatuses fall into two main types: a serial-type image forming apparatus that forms an image by ejecting droplets from the recording head while moving the recording head in a main scanning direction of the carriage, and a line-head-type image forming apparatus that forms an image by ejecting droplets from a linear-shaped recording head held stationary in the image forming apparatus.
Such liquid-ejection-type image forming apparatuses may have image failures, such as “feathering” in which dots formed with liquid droplets blur in a jaggy shape on the recording medium and “color bleeding” in which, e.g., ink droplets of different colors mix each other at adjacent areas on the recording medium to blur color boundaries. Such liquid-ejection-type image forming apparatuses may also take a relatively long time to dry droplets on a recording medium after image formation.
Hence, several types of conventional image forming apparatuses are proposed that have a liquid application device to apply treatment liquid onto a recording medium to prevent bleeding of ink on the recording medium. A conventional image forming apparatus using a liquid toner in which toner particles are dispersed in a carrier liquid, such as silicone oil or mineral oil, has a developing roller to develop an electrostatic latent image on a photoconductor and a toner application roller serving as a liquid application device to form a thin layer of the liquid toner on the developing roller. The toner application roller has grooves on its surface layer, and the surface of the grooves is nitrified.
Another conventional image forming apparatus has a liquid-amount regulation member, an application control unit, and a pressing roller as the liquid application device. In applying an application liquid to a target member, after the target material passes the liquid-amount regulation member and before the application liquid is applied to the target member, the application control unit uses the liquid-amount regulation member to regulate the application liquid on the surface of an application roller at a certain amount. The pressing roller presses the target member against the application roller to apply the application liquid from the surface of the application roller to the target member. The application control unit separates the application roller from the liquid-amount regulation member while the application liquid is not applied to the target member.
In such liquid application devices, typically, the application roller contacts a squeeze roller at a high pressure to minimize fluctuations in the application amount of treatment liquid caused by changes in the ambient environment and the transport speed of the recording medium. Such a configuration can stabilize the application amount of treatment liquid, but may reduce the application amount, thus hampering application of the desired amount of treatment liquid.